Contributions to https://mwvsciencefair.wikispaces.com/ are licensed under a Creative Commons Attribution 3.0 License. 
Portions not contributed by visitors are Copyright 2018 Tangient LLC
TES: The largest network of teachers in the world
Portions not contributed by visitors are Copyright 2018 Tangient LLC
TES: The largest network of teachers in the world
Loading...
Table of Contents
Title
Go Jibbin' With Good PostureBroad Question
How does posture affect speed?Specific Question
How do 4 different postures approaching a ski jump affect distance off the jump?Hypothesis
It is hypothesized that when the skiers are in a lower stance they will travel further off the jump. Why this is thought is because the position will offer more aerodynamics and less resistance to the wind which would slow down the skier. It is hypothesized that it will be between a standing straight stance and a fully crouched position. If you are as low as sitting on bindings, you will be leaning back more, and standing up has more resistance, so it should be between the two as they even out each other. Another reason that follows that is a skier gains speed by turning gravitational potential energy into kinetic energy of motion. A skier maximises speed by minimizing resistance to motion, both from air resistance to snow resistance. A skier minimizes his air resistance (drag) by reducing his projectile frontal area. He does this by going into a crouch position which gives him a lower drag force. Drag force acts in a direction opposite his velocity, slowing the skier down. Therefore, a lower drag force, such as a lower stance, equals a higher speed achieve. The more speed someone has, the more they will be carried off the jump.
Graph of Hypothesis
Variables
Independent Variable: Posture on skis approaching jumpDependent Variable: Distance traveled off jump
Variables That Need To Be Controlled:
Vocabulary List That Needs Explanation
attire: clothingvelocity: the speed of something moving in a given direction
projectile: projecting or impelling forward; as a projectile force
standing straight: standing up straight, not bending knees
knees slightly bent: legs slightly bent at the knees, bent over a small amount. This is a regular stance.
knees almost fully bent: knees almost bent all the way, crouched quite a bit
knees fully bent: also known as "mini-man"-sitting on bindings or crouched all the way
General Plan
In this experiment it will be determined how different skiing postures approaching the jump affect the distance travelled off the ski jump. There will be a jump set up in a backyard that is 0.71 meters high. Each tester will do four jumps on each of the four positions. At a point at the beginning of the jump marked by a food coloring line, the skier will go out of the determined stance and off the jump in a normal stance that feels comfortable to them. What will change is the positioning on the skis. Using a data table (see Data Tables), the jump distances will be recorded and the information put on a graph (see Graphs). Measuring will be done in meters from the lip (top) of the jump and mark where the center of the skiers boot hits. The four positions will be will be: standing straight, knees slightly bent, knees almost fully bent, and sitting on bindings/fully bent. Also the temperature of the snow will be found before the experiment so the snow temperature does not change drastically and alter the experiment results. It will be made sure that each skier maintains his position until the marked point on the slope and even if the skier falls the jump will still be measured where the boots hit. Using a camera (that is owned), the footage of the jump will be slowed down so the footage can allow viewing of where the boots hit. This will be compared with marks in the snow (with green food coloring) that are every 20 cm so it can be seen where the boot hit in relation to the cm tape. If the camera does not work out the same person each time will record how far the tester went off the jump by sight-he will lay next to the landing and compare the landing spot with the marks and measuring tape.Safety Or Environmental Concerns
A skier could fall and potentially be injured, but that is not likely since all of the skiers are intermediate through expert, and the jump is very small.Experimental Design
(add the correct headings from the experimental design page before beginning)Resources and Budget Table
Data Table
Time Line
3/2/12 Complete design and collection of all materials (JBES)
3/7/12 Run first official test of the set up, not collecting data, just seeing if everything works (HOME)
3/10/12 Complete all trials of experiment and all data collection (HOME)
3/25/12 Complete all data analysis; mean, median, range, graphs (HOME)
4/6/12 Complete results and conclusion writeup (HOME)
Background Research
An aerodynamic position that a ski jumper wants to get into after leaving the ski jump. The skis are kept as motionless as possible and they are pointed slightly upward. The skier has their arms down to their side and the skier is leaning forward where their torso is almost touching their skis. This position is meant to lower the wind resistance to the skier as much as possible.
When taking off from a ski jump, skiers will get in an egg position to lower their wind resistance. An egg position is when the skier gets in a crouching position, legs bent at the knees and they are also bending at the waist so their head is lower than their back and their arms are held in close to the side of their body. After take-off the skier will come out of this position into a standing position.
The jumpers rely on scientific principles developed hundreds of years ago. The first is Isaac Newton's law that any action causes an equal and opposite reaction. In the case of ski jumping, the jumper's body and skis will push some air down. The reaction from that is that some air will actually then push the skier up.
The second scientific law in play is Daniel Bernouli's discovery that air pressure drops as air moves faster. Ski jumpers who know that will position their bodies so the air above them moves faster. The slower air beneath them will have more pressure, giving the skier another dimension of lift.
There are few feats as breathtaking as a perfect ski jump. Hurtling down a snow-covered ramp at speeds in excess of 100 kilometers (60 miles) per hour, the skier literally dives off a cliff, soars through the air, and finally descends back to earth some 100 meters (328 feet) from takeoff.
To a novice, the steps in a ski jump look deceptively simple. In reality, each involves a complex balance of forces where only slight changes in equipment or body position can mean the difference between a gold medal and disaster.
Like a roller coaster, all the energy for a jump comes from __gravitational potential energy__ acquired by going to the top of a hill - in this case, the__inrun__. Coming down the inrun, jumpers try to build up as much speed as possible while maintaining control. To minimize air resistance, they get in a low crouch, point their arms forward, and bend their heads slightly downward like a diver entering the water.
Halfway down the inrun, jumpers begin to re-position their bodies in preparation for leaping off. Near the end, where the inrun begins to curve upward, they raise their hips slightly while pressing the chest tight against the knees. This makes their legs act like a coiled spring storing additional energy for the takeoff. About three meters (10 feet) from the end of the inrun, jumpers begin their final adjustments before takeoff, bringing their arms perpendicular to the ground and rising up slightly.
The most important part of the jump occurs at takeoff. Within a tenth of a second, jumpers must combine two motions at once, leaping both forward and upward at the same time. The timing of the takeoff leap is what makes or breaks a jump. If jumpers spring before they reach the exact end of the__takeoff table__, their skis will point down, causing extra wind resistance which results in a short jump. If they spring too late, their skis are pointed too high, resulting in a serious loss of control.
In the air, jumpers become flying projectiles, using their bodies and skis like a giant__airfoil__. They lean forward, producing a positive__angle of attack__ on the wind. Traditionally, jumpers always kept their skis straight in line with their bodies to lessen air resistance and reduce__drag.__ In 1989, a jumper revolutionized jumping by holding his skis in a large V with the open end pointed forward. This positioning increases the surface area below the body, providing more lift toward the end of the flight. It extends the time in the air and the distance of the jump.
References
Detailed Procedure
- The thermometer will be set up in a sunny place on the hill to ensure that the snow temperature does not change drastically throughout testing day. It will be checked after every tester does x tests for each position.
- The m measuring tape will laid out on the ground beside the jump landing area, with the beginning lined up with the lip of the jump and the rest perpendicular to the landing area.
- The camera and tripod will be set up so the landing of a tester can be viewed so as to determine where the center of his/her boot touched the ground. Then compare the place where the person landed with the measuring tape to see how far they went. If a camera and tripod do not work or are not available for use, one of the experiment directors will lay next to the jump to determine the landing spot by eye.
- The shovel and rake will be stuck into the ground beside the jump so it can be used to fix up the jump when needed so the testers all have the same jumping environment.
- The green food coloring will form a line across jump slope at the beginning of the jump to mark where the jumper should return to a normal stance for the actual jump.
- A spreadsheet is created with boxes and labels for recording the jump distances, and will use a pencil to record the numbers and a clipboard to write on.
- The food coloring will be used to make marks so it can be determined where the boot hit in relation to the m tape and record the jump distance properly.
- Now is time to gather the testers and their ski equipment (skis, boots, pole, and clothing) at the top of the hill.
- Before official results give each tester at least 5 practice jumps so they can get accustomed to the jump.
3. For the first posture test, posture #1, each tester’s name and number will be called and they will run 3 jumps in the set position. Each jumps distance will be recorded in the correct box in the spreadsheet. The order for the 4 positions will be straight, slightly bent, almost fully bent, and then all the way crouched.4. Next repeated will be step 3 for the remaining 9 testers, in order of their number.
5. Repeat steps 3 and 4 for the remaining three postures.
6. Clean up testing area, thank testers, and send everyone home.
Diagram
Photo List
A picture will be taken of the following things for our science fair presentation:Results
Means of the trials were: Standing Straight; 3.97m, Knees slightly Bent; 4.25m, Knees Almost fully Bent; 4.26m, and Knees Fully Bent; 4.25m. Knees almost fully bent was 0.01 meters (1 centimeter) further distance on average than fully crouched and knees slightly bent.
All Raw Data
Graphs
Photos
Video
Data Analysis
Conclusion
The experiment question was “How do different postures on skis approaching a ski jump affect the distance travelled off a ski jump?” Testing was whether having a low center of posture, (knees bent) or having non-displaced posture (standing straight) made one travel further off the ski jump. The independent variable for the group was posture on skis. The dependent variable was distance on skis travelled (off jump). Means of the averages were: Standing Straight; 3.97m, Knees slightly Bent; 4.25m, Knees Almost fully Bent; 4.26m, and Knees Fully Bent; 4.25m.Standing straight had the lowest amount of meters traveled (3.97) and knees slightly bent and fully crouched shared a distance of 4.25 meters. Knees almost fully bent was 0.01 meters (10 centimeters) further distance than fully crouched and knees slightly bent. Knees almost fully bent made the test subjects travel the farthest off the ski jump by 0.01 meters (1 centimeter) ahead of knees slightly bent and the fully crouched position.Discussion
The experiment question was: How does positioning on skis (stance) approaching a ski jump affect distance off a ski jump?It was answered in the experiment. The answer to our experiment question was that knees almost fully bent made testers go farthest off the jump. Some evidence to support this answer is that after we averaged the average distance for each tester for each test, knees almost fully bent had a 0.01 meter longer distance. The hypothesis was supported by the results of the experiment. The hypothesis was that knees fully bent would have the longest distance, and that was correct. The results can be explained by what was found in preliminary research. The research showed that a lower body mass (less of someone or something exposed) would result in a faster speed, and therefore a farther distance off the jump.Patterns and trends within the results were that the majority of the subjects, the lowest distance travelled was when standing straight. Examples being: JRP, ES, WB, CE, and TR. This was based on each tester’s average. There is not, however, a strong change based on on the relationship between the independent variable conditions and changes in the dependent variable. An example of this being that the Knees Slightly Bent (KSB) and Knees Fully Bent (KFB or crouched) have the same overall distance of 4.25 meters. However, like the majority of subject trials, the Standing Straight (SS) was the least distance travelled. And, like the majority of test subjects, the Knees Almost Fully Bent (KAFB) had the greatest distance of 4.26 meters, ten centimeters ahead of KSB and KFB.
Benefit to Community and/or Science
The knowledge gained through the experiment could help people that need to maximize their distance off a ski jump. An example of someone that could use this information would be the Kennett Ski Jumping Team. As they go down the starting ramp towards the jump, they need to be in an aerodynamic position that makes them go farther off the jump. The test shows that KAFB makes subjects go farthest, so maybe it would be a good idea for the Kennett jumpers to try that out. Another example of someone that could use the knowledge gained through the experiment would be freestyle skiers approaching a ski jump (they need to maximize their speed to clear the “lip” and have more air time for tricks) or ski racers in a race course (they need to maximize their speed to have a faster time). In general, the knowledge gained through the experiment would be helpful to anyone looking to go fast.
Abstract
An experiment was conducted to determine, how posture affects the distance traveled off a ski jump.It was hypothesized that the Knees Fully Bent (but not crouched) would propel the test subjects the farthest off the ski jump. The experiment question was “How do different postures on skis approaching a ski jump affect the distance travelled off a ski jump?” Testing was whether having a low center of posture, (knees bent) or having non-displaced posture (standing straight) made one travel further off the ski jump. The independent variable for the group was posture on skis. The dependent variable was distance on skis travelled (off jump). Means of the averages were: Standing Straight; 3.97m, Knees slightly Bent; 4.25m, Knees Almost fully Bent; 4.26m, and Knees Fully Bent; 4.25m.Standing straight had the lowest amount of meters travelled (3.97) and knees slightly bent and fully crouched shared a distance of 4.25 meters. Knees almost fully bent was 0.01 meters (10 centimeters) further distance than fully crouched and knees slightly bent. Knees almost fully bent made the test subjects travel the farthest off the ski jump by 0.01 meters (1 centimeter) ahead of knees slightly bent and the fully crouched position.